Newly re-elected Westchester County Executive Rob Astorino, a Republican, paid a surprise visit to the all Democratic Somos El Futuro gathering of state politicians in Puerto Rico last week, delivering an address in fluent Spanish and impressing many who were there.

Gov. Cuomo, by contrast, skipped the event, disappointing many and reinforcing his image as aloof from, and even contemptuous of, his fellow Democrats.

Astorino’s visit wasn’t by accident. The Post has learned that he told several aides and key fund-raisers in recent weeks that if he won last week’s election by a comfortable margin, he would “seriously consider” challenging Cuomo next year.

He won by a landslide in a heavily Democratic county within the critical New York City media market, and challenging Cuomo is exactly what he said he is considering in an expansive telephone interview with The Post from Puerto Rico.

“I am considering it right now. I have to consider it,’’ declared Astorino. “New York is hemorrhaging jobs, I think we just went from 49th to 50th in terms of a bad business climate. We’re going in the wrong direction.

“I feel New York is fundamentally out of balance right now with extraordinarily high taxes, a terrible regulatory climate and an explosion of Medicaid and pension costs that is really killing counties, local governments and school districts. There have to be some fundamental changes going forward,’’ he added.

Astorino has been working on developing a range of policy positions that would be important in a statewide race for governor.

He said, for instance, that if he did become governor, he would move to create thousands of private-sector jobs by approving “with proper restrictions’’ drilling for natural gas — known as “fracking’’ — in the economically hard-pressed Southern Tier, something Cuomo, facing threats from radical environmentalists, has refused to do for three years, despite promises that he would.

Astorino did credit Cuomo with “baby steps’’ to improve the state’s economic picture during his first year in office.

And he conceded that the governor, who is popular with all but upstate voters, would be difficult to beat, saying, “He’s certainly the prohibitive favorite.’’

A key GOP source said Astorino, a media-savvy former radio broadcaster and journalist, has been promised strong financial backing “by several financial heavy hitters’’ if he challenges Cuomo.

In last week’s contest, Astorino defeated New Rochelle Mayor Noam Bramson with 56.5 percent of the vote in a 2-1 Democratic-leaning county.